An Evaluation of Lignosulfonate as a Sacrificial Adsorbate in Surfactant Flooding

Abstract

Summary A study was conducted to investigate the feasibility of using lignosulfonate as a sacrificial agent in the surfactant flooding process. An analytical technique based on high-performance liquid chromatography (HPLC) analysis was used to determine the concentration of lignosulfonate and petroleum sulfonate. Lignosulfonate and petroleum sulfonate adsorption isotherms were established and used to assess the sacrificial effect of lignosulfonate. A simple model to describe the ion exchange in the presence of lignosulfonate was developed. This model includes the presence of lignosulfonate was developed. This model includes the association of cations with lignosulfonate. The main results of this study are as follows. First, surfactant loss can be reduced significantly (is greater than 50% reduction) by pretreatment with a lignosulfonate preflush. However, no significant pretreatment with a lignosulfonate preflush. However, no significant reduction is obtained when lignosulfonate is incorporated with the surfactant slug. Second. more cations are exchanged from the rock in the presence of lignosulfonate. This enhanced carbon exchange is a result of presence of lignosulfonate. This enhanced carbon exchange is a result of the association of divalent cations with lignosulfonate. Third, lignosulfonate causes dissolution of soluble minerals to a much greater extent than brine or petroleum sulfonate, producing undesirable divalent cations. Finally, the brine tolerance and optimal salinity of petroleum sulfonate are not greatly affected by lignosulfonate. From these laboratory results, we conclude that lignosulfonate has potential as a sacrificial adsorbate for surfactant flooding. Introduction One of the major factors affecting the economics of surfactant flooding is the adsorption of surfactants onto reservoir rock. Adsorption can cause excessive depletion of surfactants from the surfactant slug, resulting in decreased efficacy to mobilize oil. Also, chromatographic separation of the surfactants can result from the selective adsorption of surfactant components. Because the surfactant slug comprises various surfactants and is an optimum formulation for oil recovery. chromatographic separation will impair the solution stability and the oil recovery efficiency. In the past, research has been focused on the determination of the adsorption mechanism and the effects of numerous process parameters. As a practical approach for the reduction of surfactant loss, many studies have been conducted on the use of sacrificial agents and cation-sequestering chemicals-such as sodium carbonates, sodium tripolyphosphates. ethylenediaminetetraacetic acid (EDTA), silicates and lignosulfonates-in chemical flooding processes. These chemicals may be included in the preflush with a NaCl brine or may be added to the surfactant slug. The objective of this work was to evaluate the use of lignosulfonate as a sacrificial agent for surfactant flooding. Although the use of lignosulfonate as a sacrificial adsorbate was proposed in patents, very little work has been reported Only one field test using lignosulfonate with surfactant flooding was reported in the literature. Lignosulfonate is a byproduct of the paper industry and is much cheaper than petroleum sulfonate. Because lignosulfonate carries anionic charges in solution. it can reduce the surfactant adsorption sites of reservoir rock. thus acting to protect the primary surfactants in the surfactant flooding process. To investigate the feasibility of using the lignosulfonate as a sacrificial adsorbate in surfactant flooding, the following performance properties were tested:effect of lignosulfonate on surfactant adsorption.effect of lignosulfonate on cation exchange and mineral dissolution, andbrine tolerance and compatibility of lignosulfonate with petroleum sulfonate. Experimental Procedure A blend of Petrostep 465 and 420 TM was used as the primary surfactant. An equal weight of each sulfonate on primary surfactant. An equal weight of each sulfonate on a 100 % active basis was used. The surfactant blend contained isobutyl alcohol and NaCl in concentrations of 10 g/kg unless otherwise stated. Throughout the paper, concentrations are expressed as the weight of solute in a unit weight or volume of solution. The lignosulfonate employed was Petrolig ERA-27 TM (ammonium lignosulfonate). This lignosulfonate contained 2 g/kg of calcium. Unless otherwise stated, the concentration of NaCl in lignosulfonate solution was 10 g/kg. Lignosulfonate solutions in their original acidic state (pH =4 as received), as well as solutions neutralized with 50 g/kg of NaOH, were used in this study. SPERE P. 17

Enhanced oil recovery by alkaline-surfactant-alternated-gas/CO2 flooding

“…With better foam performance, the residual oil in unswept zones was displaced leading to an improvement in oil recovery. Na-lignosulphonate, the main constituent of BL, has been known to act as sacrificial agent during CO 2 foam flooding process (Hong et al 1987). Injecting BL with SDS had most likely reduced SDS adsorption by rock grains, maintaining the foaming ability of the SAG process.…”

Cost Reduction and Injectivity Improvements for CO2 Foams for Mobility Control

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